The invention relates to neutron and x-ray radiography apparatus and more particularly to apparatus for use in nondestructive radiography for producing neutrons and x-rays with a relativistic electron beam pulse.
Welds on structures such as ship hulls, bridges, metal building frames, and the like, for safety should be examined for integrity. An apparatus in accordance with the present invention can be used to nondestructively radiograph such structures to verify their welds and other desired features. The invention may be practiced with portable devices making inspection far easier than with existing devices which are large, cumbersome and expensive. Existing devices also require an accessible external power source, whereas an apparatus in accordance with the invention contains its own power supply. It is therefore easy to use the invention at remote locations.
Conventional radiography devices provide penetrating radiation by bombarding an anode target with high energy electrons emitted from a cathode. Relatively low-voltage portable x-ray devices are shown in U.S. Pat. Nos. 3,643,094, issued Feb. 14, 1972, and 3,783,288, issued Jan. 1, 1974, with operating voltages at about 100 kV and 350 kV, respectively. The production of higher voltages, however, conventionally requires equipment which is not portable.
Magnetic flux compression generators (MFCGs) can be designed for portability, however, and generate relatively high voltages. A series of explosively driven magnetic cumulation generators used to produce a high voltage is disclosed by A. I. Pavlovski et al. in "Transformer Energy Output Magnetic Cumulative Generators," Proceedings of the Second International Conference on Megagauss Magnetic Field Generation and Related Topics (Plenum Press, New York, 1980). A capacitor bank or permanent magnet is used to generate a first magnetic field. That first magnetic field and subsequent fields are rapidly collapsed using explosives to produce a high voltage output which is coupled to a load with a transformer. Pavlovski et al. teach cascading MFCGs for energy amplification. No particular load application is taught, and voltage levels to only about 400 kV are taught.
A relatively high power diode is a diode structure generating a relativistic electron beam. Such a device typically requires an operating voltage about 1MV for generating the relativistic beam. However, conventional relativistic beam diodes tend to generate a plasma layer adjacent the cathode due to work function heating as electrons are emitted from the cathode. The low resistance associated with the plasma would conventionally prevent a flux compression generator from reaching the high voltage levels for relativistic beam operation.
These and other problems of the prior art are addressed by the present invention and a portable radiography apparatus is provided with flux compression generators supplying high voltage to a relativistic beam diode.
Accordingly, an object of the present invention is to load a compression flux generator with a relativistic beam diode.
Another object of the present invention is to preclude generation of the diode electron beam until a maximum voltage is output from the compression flux generator.
One other object of the present invention is to provide portable nondestructive neutron and the x-ray radiography.